In the related art, a composite molded body in which a metal member and other members (for example, a molded resin member) adhere to each other so as to be integrated has been used in many industries. However, in this type of composite molded body, boundary surfaces of the metal member and the other member, which come into contact with each other, do not adhere to each other and a minute gap is generated by changing a solidification process or an environmental temperature of the other member. Thus, a problem occurs in that ensuring of sufficient adhesion and airtightness is impossible. In order to solve this problem, a technology in which a surface of the metal member is roughened, that is, unevenness is provided in the surface of the metal member, and thus, adhesion between the metal member and the other member is improved has been proposed.
In this type of technology, a technology disclosed in Patent Literature 1 is present as a technology of roughening the surface of the metal member by irradiating the surface of the metal member with an energy beam such as a laser beam. In this technology, irradiation with an energy beam having high energy density causes the surface of the metal member to be melted, and a sputter causes droplets of molten metal to be scattered from the surface of the metal member. Thus, an uneven portion is formed by solidifying the droplets of the molten metal, and thus, a rough surface is formed. Here, in order to cause sputtering to occur in this manner, irradiation with an energy beam having high energy density of, for example, 300 J/cm2 or more is required in addition to a material of the metal member. In this technology, a continuously oscillated laser beam is used as the energy beam.
The technology of roughening the surface of the metal member is also used for suppressing expansion of solder in, for example, a composite molded body in which other members (for example, electronic components) are bonded to the surface of the metal member through the solder. In such a composite molded body, a problem that the solder is expanded when other members are pressed on the molten solder which is provided on the surface of the metal member easily occurs, for example, during manufacturing. Thus, the surroundings of a portion of the surface of the metal member, at which the solder is disposed is roughened (unevenness is formed in a surface) and unevenness which is formed through roughening causes expansion of the solder to be blocked. Thus, the expansion of the solder is stopped. In this case, the size (height or width of a convex portion) of the unevenness is set to about several μm such that the unevenness causes the expansion of the solder to be blocked.
The technology in which the surface of the metal member is irradiated with an energy beam such as a laser beam, and thus, the surface of the metal member is roughened is also used when the unevenness is formed in order to suppress expansion of the solder. In this manner, when an unevenness having a large size of about several μm is formed, irradiation with an energy beam having high energy density (for example, 300 J/cm2 or more) is required.
In the above-described technology disclosed in Patent Literature 1, droplets of molten metal are necessarily scattered, and the droplets of molten metal may be scattered at a portion other than a portion of the metal member, at which irradiation with an energy beam is performed, or a portion on the outside of the metal member. Thus, various inconveniences may occur. In addition, since an energy beam having high energy density is used, energy consumed by processing is increased.
Particularly, when a configuration in which a metal thin film is provided, and the metal thin film is formed by plating a metal member on a surface of a base, if a surface of the metal thin film is roughened by using the technology disclosed in Patent Literature 1, the applied energy beam has high energy density, and thus, a situation in which the metal thin film is penetrated easily occurs. If the metal thin film is penetrated and the surface of the base is exposed, oxidization of the base and the like, which causes inconvenience, occurs.